Blood Lactate Concentration Following Exercise: Effects of Heat Exposure and of Active Recovery in Heat-Acclimatized Subjects

Abstract

The purpose of this study was to examine the effect of ambient heat on the decrease in blood lactate concentration ([LA]_bl) during passive and during active recovery. Ten trained men performed six 1 -min bouts of exercise at 100 % VO₂peak on a cycle ergometer, with 1-min rest between the bouts. Each subject exercised twice in thermoneutral (22 °C, 40 % RH, TN), and twice in hot (35 °C, 30 % RH, H) conditions. Exercise was followed by either 40 min of passive recovery (sitting) or by 20 min active recovery (cycling at 35 % VO₂peak) and 20 min passive recovery, named thereafter, 'active recovery'. Capillary blood lactate was measured before, 1 min after, and every 5 min during recovery. Heart rate (HR), rectal and skin temperatures (T_re, T_sk) were monitored continuously. VO₂ was measured prior to exercise, during the last exercise bout, the first 10 min of recovery, and periodically thereafter. Post-exercise [LA]_bl was similar in all treatments (13,5 + 1.8, 13.0 ± 1.3, 14.8 ± 4.1, 13.3 ± 2.6 mmol · l^-1 for TN-active, TN-passive, H-active and H-passive, respectively). [LA]_bl was significantly lower during active, compared to passive recovery in both, TN and H conditions. Environmental heat did not independently affect [LA]_bl during passive or active recovery. Exercise resulted in an elevation in T_re in all treatments, with a significantly higher T_re during active recovery in H compared to the other sessions. Likewise, no differences in HR and in VO₂ were observed between H and TN conditions during active nor during passive recovery. In summary, under the conditions of this study, ambient heat does not affect the rate of decrease in [LA]_bl. As in the TN condition, active recovery in the heat results in lower [LA]_bl. However, this is accompanied by a higher T_re in ambient heat.

Key words

Cycle ergometer - lactate metabolism - thermoregulation